1. Field of the Invention
The present invention relates generally to a method of manufacturing a foam article having an outer surface covered by a suitable skin member, and more particularly to a method suitable for producing a head rest or head restraint for an automotive vehicle, which has an annular construction.
2. Discussion of the Prior Art
In the art of designing a head rest or head restraint for motor vehicles, which is a foam product whose outer surface is covered by a suitable skin film or tube, there is an increasing tendency of providing an opening in a central portion of the foam mass of the head rest body, thereby causing the head rest to have an annular configuration. In the manufacture of this type of head rest, there has been an attempt to enhance the appearance and quality of the head rest, by covering the outer surface of the foam body with a tubular or toroidal skin or bag. This tubular skin is formed of skin members of a suitable material, such as fabric members or synthetic leather members, that can be sewn, fusion-welded or otherwise joined into a tube or bag.
On the other hand, the head rest having an annular construction with a central opening requires a relatively rigid, annular core structure embedded therein, for the purpose of reinforcing the foam body and attaching the head rest to a seat of a vehicle. In the presence of this annular core structure, known methods of manufacture used for a conventional non-annular head rest are not suitably applicable to the manufacture of the annular head rest which uses the above-indicated skin members for the tubular skin. That is, the practice of the known methods for the annular head rest results in a significantly deteriorated appearance of the head rest, and a loss of high-quality feel of the head rest, for the following reasons.
Described more particularly, an example of the known methods wherein a non-annular head rest is produced by using skin members which are joined together into a skin bag, includes the steps of: preparing the tubular skin having an unjoined portion corresponding to the lower side of the head rest, by joining together the skin members with their nominal insides exposed outwardly of the obtained skin bag; inserting a suitable core structure into the prepared skin bag through the unjoined portion of the skin bag; closing the unjoined portion of the skin bag so as to completely enclose the core structure inserted therein; injecting an appropriate foamable material into a cavity or space formed between the skin bag and the core structure. Thus, the cavity is filled with the foam body formed of the injected material. If this known method conventionally used to produce the non-annular head rest is applied to the manufacture of the annular head rest, it is required that the skin members be left unjoined at the entire inner periphery of a tubular skin defining the central opening of the head rest, in order to permit the core structure to be inserted through the unjoined portion into the tubular skin or bag. Therefore, it is necessary to join the unjoined portions of the skin members, on the outer surface of the tubular skin after the core structure is set in the tubular skin. Thus, it is unavoidable that the seams or joined portions or edges of the skin members are exposed on the inner periphery of the tubular or toroidal skin which defines the central opening of the head rest. For this reason, the appearance and high-quality feel or image of the produced head rest are considerably deteriorated.
A solution to obviate the above problem with the conventional method for manufacturing a foam product is disclosed in laid-open Publication No. 62-35811 of Japanese Patent Application, wherein two joining plates are disposed along mating portions of the skin members, such that the two joining plates pinch the mating portions of the skin members therebetween, thereby joining the mating portions. Although this method disclosed in the above Publication is capable of producing an annular head rest having an improved appearance and an excellent high-quality feel, the use of the joining plates pushes up the cost of manufacture, and reduces the soft cushioning property of the head rest during its use.